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The water-sensitive effects of fine conglomerate and pebbled coarse sandstone reservoirs in the Lower Triassic Baikouquan Formation in Mahu Sag in the Junggar Basin are evaluated, and the main controlling factors and patterns are analyzed. Based on basic physical property tests, rock and ore composition analysis, pore structure analysis, and water-sensitivity experiments, the water-sensitivity effects of different lithologies are evaluated to determine the main controlling factors. Moreover, the sand-filling model is used to conduct a single-factor study to verify the accuracy of the analysis of main controlling factors of water sensitivity. The results indicate that the physical properties and pore structure of fine conglomerate are poor, yet its throat sorting surpasses that of pebbled coarse sandstone. In the study area, mineral hydration expansion constitutes the primary factor causing water sensitivity damage, while fines migration represents the secondary factor. Although the favorable physical properties of pebbled coarse sandstone increase the probability of contact between clay and fluid, its poor throat sorting and cementation degree tend to induce throat blockage, consequently resulting in a significantly higher water sensitivity index compared to fine conglomerate. Permeability serves as the primary controlling factor for the water sensitivity effect. In reality, the sensitivity index of fine conglomerate increases sharply with the increase of the Klinkenberg permeability, while that of pebbled coarse sandstone decreases gradually with the increase of the Klinkenberg permeability. The rationality of this primary controlling factor is verified through the single-factor analysis of the sand-filling model. Due to the synergistic effect of permeability and wettability, there is no significant difference between the initial damage rate and the secondary damage rate for fine conglomerate, However, the initial damage rate of pebbled coarse sandstone is significantly greater than the secondary damage rate.
| Country | China |
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